The Provenge prostate-cancer treatment uses a patient's own immune system to kill tumors. Doctors extract immune cells called antigen-presenting cells (APC) from a patient's blood and, in a lab, expose them to prostatic acid phosphatase (PAP), a molecule th at only prostate-cancer cells produce. Injected back into the patient, the modified APCs seek out any cells that express PAP and instruct the patient's immune system to kill the cancer cells.
Clinical trials of terminally ill patients for whom no other treatments have been effective have shown that Provenge can extend life by four months on average, and up to three years in some cases. Scientists at Dendreon and elsewhere are working to apply the technique to other types of cancer.